1. Field of the Invention
The present invention relates generally to the field of metal-cutting machine tools, and more particularly is concerned with a novel dovetail shaper metal-cutting tool.
2. Description of the Prior Art
A dovetail shaper metal-cutting tool is utilized in a chip-type machining process to cut a dovetail-shaped slot into a workpiece. An illustrative dovetail shaper metal-cutting tool 10 of the prior art is illustrated in FIG. 4. Prior art tool 10 is utilized in Mitsubishi SC 25 CWC Shaper Cutter machine to cut a dovetail slot having a dovetail angle of 70.degree. into an overdrive gear for a manual transmission. FIG. 3 illustrates a partial segment of a representative manual transmission overdrive gear 26 that has had a dovetail slot 28 cut amidst spline teeth 29 of the overdrive gear. The tool tooth illustrated in FIG. 3 is that of the present invention, however, and is not a tooth of prior art tool 10.
Prior art tool 10 has six teeth, two right hand dovetail cutting teeth 14, two left hand dovetail cutting teeth 12, and two square bottom cutting teeth 16. A dovetail slotting operation utilizing prior art tool 10 requires the use of three cutting teeth during three distinct cycles: a right hand cutting tooth 14 to form the right hand taper of the dovetail slot, a left hand cutting tooth 12 to form the left hand taper of the dovetail slot, and a square bottom cutting tooth 16 to form the squared bottom of the dovetail slot.
Experienced machine operators have found it difficult to maintain the desired dovetail angle on both sides of the dovetail cut and to machine the bottom of the dovetail cut perfectly flat when utilizing prior art tool 10 in a Mitsubishi SC 25 CWC Shaper Cutter machine. As many as eleven machine adjustments are necessary to set up this machine to properly orient the cutting teeth 12, 14, and 16 of prior art tool 10 to obtain the desired dovetail slot, and an illustrative cycle time necessary to complete a specified dovetail cut utilizing three cutting teeth of prior art tool 10 has been approximately 5 minutes. When in operation, no readily discernible evidence exists on the workpieces to alert the Machine operator that dovetail angles made by the cutting teeth 12 and 14 of prior art tool 10 may have exceeded acceptable tolerances or that a bottom cut is not perfectly flat.
Furthermore, the dovetail cut made with prior art tool 10, even when within acceptable tolerances, has not been pleasing to the eye, due to the necessary formation of tear drops in the dovetail cut resulting from right and left hand cutting teeth 12 and 14 cutting deeper into the workpiece than a bottom cutting tooth 16. This is done to avoid the formation of unacceptable ridges at the points where the left and right tapering dovetail cuts intersect the bottom square cut.